True rate of turn instruments



July s, v1952 w. WRIGLEY TRUE RATE OF TURN INSTRUMENTS Filed sept. 17, ,194e

5 Sheets-Shea?A l INVENT R 149mm EY BY j /gTToRNEY WAL TER July 8, 1952 w. WRIGLEY 2,602,239

TRUE RATE OF TURN INSTRUMENTS Filed sept. 17, 194e 3 Sheng-sheet 2 INVENTOR WALTER VVR/@LEV July 8, 1952 w. WRIGLr-:Y 2,602,239

l TRUE RATE 0F TURN INSTRUMENTS Filed sept. 17, 194e 's sheets-sheet a INVENTOR l WHLTER VVR/@LE MAT'TORN EY.

atentec'l juy 8, 19.52

UNITED STATES PATENT OFFICE Walte Wiig1ey,- Wnstoni, Majss';,iassisiitr. tu' rufe" Sperry Corporation,- a corporation of Delaware situata-17, 194i,-

" tiene 9 cia-itis. (ci. 534:26@

p tuin of they vehicles on windu niet are enlisted'. amuse vim measir of the rat ofy yt'vina out an a s per# une trainen wriietyit is mounted 'and' not rsf it@ tft f trie "afrit azimuth,- other` ivettnj 'ate tf tuffi-e win site' utput which is a true banks in making a turn, an error due tothe" barili angle enters the output of the rate gyro and causes a false output qr'ijidication. In the extreme case of a 90 bank angle the gyro ceases to operate as a turn-.indicator and. no indication is scud'beeaus'ethe gyra' spin aids' would be in a verticali position.' However,- .the instrument would-be' accurate up to steep bank'anglesV such as 60 or 70 degrees, if theoutput 'orindication is corrected'. as hereinafter explained.` l

If'we let Rf be the' rate of turn of the craft abouta' Vertical axis relative'totiie earth yand let @lbethe bank angle/of theV craft as it turns about this vertical axis; then the' amount of precess'ion ofythe gyro under the usual resilient restraint will .be proportional to the product R.' cos 0. Therefore the indicated" rate of turn wi111be'di=' minishedby a' cosine function of the bank angle; By my invention I'v eliminate" this error .by ob= taininga signal Wiriichr is equal to the'reciprocalA of the cosiefunction, i.- e., a secant functinofthe bank angle and modify the gyro outputby this sec'ant function.

According to my invention 'I' therfore'pr'ovide amais for effectively correcting. thev cosine of the bank angleerror in the 'output f the rate gfyi'and` thereby give' any utput Which 'is a' measure of rat of turn about true'trtieal i. e.; 'an' axis' coincident f with" the direction in which gravity acts.

Aotherfeature'of the invention isto prot/idea rate of turngyro instrument, the'output of'vvhich is modied by an amount proportional to' a trigonometricy function'. of .the bank'- angle i; the outputof the rate ofturngyro is multiplied bythe-reciprocal of the cosineof th'ebank angle orbyit-s equivalent, thsecant ofthe 'bank angle.

@111 s @sans journaled on a horizontal axis normal to said spin axis. The rotor 2' is shown as being air driven as by nozzle Il which is connected to some source of pressure (not shown). The rotor bearing frame 3 is journaled on the fore and aft horizontal axis of the craft by means of leaf springs 5, at the one end of the casing, and by leaf springs 3, E at the other end thereof, one end of the springs being fastened at the periphery of the casing and the other ends being secured to the rotor bearing frame trunnion shafts l', i. The precessional rotation of the shafts l', l" is restrained by leaf springs 5, 5', 6, E and this limited rotation is proportional to the rate of turn of the craft but diminished by a cosine function of the bank angle. .The gyroscope 2 is liquid damped as by means of damping discs 8, 8 fastened to the rotor bearing frame 3 and located in liquid containing end walls 9, 9 of the instrument housing I.

For a more detailed description of the gyroscopic element of this invention, see the aforesaid Draper reissue patent.

In the present invention it is desired to effectively modify the output or indication of the instrument by correcting the error produced by the bank angle of the craft on which itis mounted, that is, by-eliminating the cosine function of the bank angle factor. As stated above, this may be done by obtaining a signal which is proportional to a reciprocal function of the cosine of the bank angle, i. e. a secant function, of the bank angle of -the craft. It has been found that the resultant acceleration of the component of centripetal acceleration and the component of gravitational acceleration along the normally vertical craft axis is proportional to the secant of the bank angle. The above may be more fully understood by referring to copending application Serial No. 682,602, filed July 10, 1946, now Patent No. 2,553,560, in the name of Orland E. Esval for Aircraft Turn Control. This factor is then` interposed between the output shaft of the gyroscopic element and the indicator or output of the instrument and modifies the latter to give an output which is proportional to the true rate of turn of the craft.

,To accomplish the above result, I have shown a gear IIJ mounted on the gimbal trunnion shaft 'I and rotatable therewith. Gear I0 meshes with gear I I which is journaled in a downwardly projecting bracket i2 at the top ofthe instrument housing l. A sector I3 (see Fig. 2) is mounted for rotation with gear -I I and frictionally engages a wheel Ill which is free to rotate and also free to move up and down along a guide rod I5. The guide rod I5 is supported at its top from the bracket I2 and projects downwardly along the vertical axis of the instrument and is supported at its lower end by the housing l The wheel I4 is translatable alongsaid guide I5 by the action of a mass I6 which is, in turn, supported by a spring I1 and thrust bearing I8. Between the Wheel I4 and the mass I6, an integral therewith is an elongated pinion I9 which engages with a sector gear 28. This sector gear .is shown as mounted on a shaft 2l, supported for rotation in a bracket 22 which projects upwardly from the base of the instrument housing I. At the lower end of shaft 2l is a pair of bevelled gears 23 `which rotate an output shaft 24 which has fixed thereto at its outer portion an indicating device shownk as a pointer 25 Vand suitably calibrated scale 2t (see Fig. 3). V

The mass I 6 is shown as being'enclosed in a aeoaase liquid containing case 21, said case forming a damping means for the mass I6 whereby the mass will respond only to long period accelerations and not to short period accelerations such vas may be caused by turbulent air. The wheel I4, mass i5, spring I'I and pinion I9 together form a spring suspended, fluid damped accelerometer which is mounted to act along a normal to the floor of the aircraft and to measure the magnitude of the above-mentioned resultant acceleration. The magnitude of the resultant acceleration equals the acceleration of gravity multiplied by the sec-ant of the bank angle, and the instrument correction is effected by the mass and spring combination which is responsive thereto. The mass and spring factors, being constants, may be ascertained by proper instrument design.

In operation, when'the airplane banks the rotation of the gyro output shaft 'I is proportional to the rate of turn diminished by cosine 9 (the bank angle). In other words, the rate gyro output on shaft 'I has a rotation which would indicate less than the true rate of turn, but the action of the acceleration sensitive mass It pulls down the wheel I4 increasing, through the change of radius between the wheel I4 and the axis of rotation of the friction sector I3, the effective rotation of the output shaft 24. This action, in effect, increases the motion transfer ratio between the gyro output on shaft 'I and the instrument output shaft 24. The amount of displacement of the acceleration sensitive mass IS, measured from the pivot of sector I3, is as above pointed out, made proportional to the secant of the bank angle and therefore the indication provided by pointer 25 and scale 26 is proportional to the product (qb cosine 6) times (secant 0). Since the secant 0 is equal to cos 0 the cosine factor present in the output ofthe gyro cancels out the cos 0 factor and the modified output appearing at shaft 24 is independent of the bank angle and so is a measurek of the true` rate of turn of the craft.

In Fig. 4, there is'shown another modification of the invention wherein the acceleration sensitive means I6 is shown as mounted directly on the output shaft 'I of the gyro 2. In this case, the acceleration sensitive element is shown as a mass 30 connected by leaf springs 30', 30" which are riveted to the mass 3G and the block 3l, said block being fastened directly to the gyro output shaft 7.Y To provide damping of the acceleration sensitive element used in this instance, there is provided between the mass 3G and the block 3I and the leaf springs 3D', 3B, resilient piece of rubber 32.

Attached to the mass 3B] is a downwardly projecting arm 33 which has on the end thereof a pin 34 which rides in an elongated slot 35 in a lever arm 36.

in Fig. 4, when the mass 35 is acted upon by.`

the above-mentioned resultant acceleration force dueto banked turning of the craft, it carries 'm downwardly thearm 33 and pin 34, and effectivea substantiallyv The mass is permitted to moveV only along an axis that is substantially parallelv As in the case of Fig. 1, there may .Y

ganarse lyV increases themovement ofthe pointer ZE, which has been displaced by the pre'cession of the gyro,4 by changing the fulcrum Lofthe lever arm 36.

The modification shown in Fig. 6 is vdifferent from that shown in Figs. l and 4 in that in this case -there is no sliding friction involved. The increased motion transfer ratio between the gyro output shaft 1V and the movement of indicating pointer 25 is accomplished by a series of cross spring hinges of known type.

In this case, the'pivot axis 42 of the pointer 2-5'- -is vdefined by pairs of flat cross spring hinges 40 and 40', and 4I and 4i. These springs permit the'rotation ofthe pointer about the axis 42l'while at the same time restraining-the translation ofthe pointer. Attached to the output shaft 1 -of thefrate -gy-ro an arm 43 whichat its 4ripper end has connected a flexible spring 44. Flexible spring 44 is in turn connected toa frame 4B on which are also fastened the cross springs 40, 40 and 4|, 4|. These flat springs are fastened to the acceleration sensitive means I6. This-'means is shown as a mass 41 mounted on the instrument housing i by sets of leaf springs 48, 48'and 49, 49 and can be dampedby means similar to that shown in Fig. 4. It is obvious from lthe drawing that the mass 48 is free to move verticallywith respect to the craft-and yet is restrained by its mounting springs from translational movement parallel to axis 42. A small mass dcounterbalances the arm 43, pointer 25 and -spring 44 together with the frame 4'5.

In operation when the mass 41 moves down n due vto accelerations along the vertical axis of the craft during a banked turn it carries with itfthe cross springs 40, 4U', 4I, 4I the iiat spring 44 vand vframe 46; therefore, the lever arm between the arm 43 and the/axis 42 of the pointer is shortened, thereby increasing the displacement of the pointer 25'. Again, the amount of displacement of the mass 47 is proportional to the secant of the bank angle and, as inthe apparatus of yFigs. 1 and 4, the output of the instrument is increased as the secant function of the bank angle.

lin Fig. 8 there is shown a modicationwherein the'acceleration sensitive means generates a voltage which is proportional to the secant of the.

' bank angle and this voltageV is applied to an electrical pick-off on the rate gyro and ymodifies the output of this pick-off to give a voltage which is proportional to the azimuthal rate of turn ofthe craft.

In this case, the acceleration sensitive means IB" has a -mass 5I attached to the housing i by' means of at springs 52 and 53 whichA limit the 4displacement of the mass 5l along the vertical axis of the craft.

To provide a voltage which is proportional to the secant ofthe bank angle, there is provided a.C -type pick-off whose armature 54 is secured tothe. mass 5I` and movable therewith, and cooperates with the C-shaped corev 55 upon each leg of `which `there are windings 56 and 5l. The winding 56 on one of the legs of the pick-01TV is energized from a source `of constant alternatin g voltage and the winding `5'! on the other leg has a vvoltage induced therein by the relative displacement of the armature 5 4 between the two legs, The armature isadjusted so that at one-g afcertain voltagej exists inthe winding 5T and anyaddition to Ag wil-l produce an increased voltag ifi Winding, .511 .Sne the secant 'ofiananele is never'less than'unity, thee-pick-#off is adjusted 6. to produce .an initial lvoltage output equal t some arbitrary value, say unity,'whenfthe ac, celeration along thev vertical craft axis isv gravity alone; but the G-pick-off Lvoltage output will increase linearly with :displacement of .its armature so that the voltage output ofV the accelerometer ywill V-aryf with displacement of its armaf ture which is responsive to theresultant'accelera-A tionvacting on the armature mass which,. in turn,

is equal to the acceleration of gravity 4multiplied by the secant of the bank angle.

They output shaft 'l ofthe gyro 2 controls in this instance an electrical picky-off 59 which gives an output voltage which is proportional to vthe rate :of turn of the craft aboutA the vertical craft the relative displacement of the armature 'of' the pick-off'. Therefore shaft 'if carries an arm V60 at the end of -which is secured an armature riii. Armature 6I cooperatesA with the E transformer 62 which is fixed yrelative to the armature 6I.

' The output voltage of the C transformer l55 appearing on leads 63 is fed' to an amplifier. where it is amplified and usedto energize/the central leg ofthey E transformer 6.2. This energizing voltage will vary as the secant of the bank angle and therefore the output of the instrument appearing on leads 65 will beproportional to the rate of turn value measured by the. gyro multiplied bythe secantofthe bank angle.

There is shown in this gure a .phase sensitive.

rectifier 66 into which they voltage appearing on.

leads 65 is fed for so adjusting the voltagethat it may vbe fed to an indicatingv mechanism EL here; shown. as a meter, which gives. a right. left' indication which is proportional fto the. rate. of turn in azimuth of the craft.

Itisv tobe understood that the. voltage appear-- ing on leads 65`may be used to apply a signal proportional to thetruerate of turn of the craft .to any'remote apparatus on the craft, suchas an au. tomatic pilot, which requires an alternating cur,- rent voltage. Of course,v the. output ofthe phase. sensitive rectifier 66 couldbe used similarly by an apparatus v /hi'ch requires. a D. C. voltage inv its operation. A v

InFig. 9. there is shown a modification where-- inthe bank angle of. the craft is actuallymeas.-V ured by a gyro vertical. A secant. function of this measuredl bank angley is then induced into; the Output-ofthe;rategyro to modify itandmakez l it proportional to the azimuthal rate of; turn;

For this. purpose there is shown a, gyrovertical 10= which -will give a direct measure of 'the bankA substantially less` than because corripensation for the errorA caused by bankl angle ofthe type disclosed in this invention will only be effective upto bank anglesV of say 60 to 70 degrees.

Cam follower T2 has xed thereon a 'slider 13 which cooperates with a potentiometer or, rheostatu. The displacement' ofthe slider'13 causes afresistancedrop in the rheostat and' therefore an-increase inthefvoltage appearing on theleads acoaeso` '15', this increase being proportional to the secant of the bank angle. i

As in Fig. 8, the outputshaftl of the rate gyro 2 controls-,the output of. anv E transformer 59.

However, the' central leg thereof is excited by an A. C. voltage from the source 58. The output ofthe Evtransformer 59' is connected in series with the rheostat HlV and therefore, the voltage appearing on leads 16 is an A. C. voltage which is proportional to the azimuthal rate of` turn of the craft.

As in Fig. 8, there is also shown a phase sensitive rectier 66 which produces a D. C. signal that is applied to a meter 67' similar to that shown in Fig. 8. Similarly, the voltage appearing at I6 or S6 may be applied directly to an automatic pilot or other apparatus on the craft requiring a voltage which is proportional tothe A azimuthal rate of turn of the craft. Y

Since many changes could be made in the above construction and many apparently widely diiferent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. ln a true rate of turn indicator having an indication proportional to therate of turn in azimuth of the craft on which it is mounted, the combination with a rate of turn gyro, of acceleration sensitive means adapted to give a displacement along the vertical craft axis proportional to a function of the angle of tilt of said axis, of an indicator member, of motion transmitting means `comprising a flat sector operatively connected with said rate gyro, and a rotatably mounted member in frictional engagement with said sector and radially displaced on said sector memberaccording to thedisplacement of said acceleration sensitive means, said rotatably mounted member being operatively coupled to said indicator member.

2. n a rate of turn indicator having an indication proportional to the rate of turn in azimuth of the craft on which it is mounted, the combination with a rate of turn gyro, of acceleration sensitive means adapted to give a displacement proportionalto the resultant acceleration of said craft along the vertical craft axis and op- 3. Ina rate of turn instrument having an output signalv proportional to the rate of turn in azimuth of the craft on which it is mounted undi-V minished as a function of the bank angle of said craft,l the combination with a rate of turn gyro, of means responsive to the resultant acceleration of said craft along the vertical craft axis forfpro'- ducing a signal proportional to said resultant acceleration, and means controlled by said signal producingrmeans for compensating for the eife'ct of attitude of the craft infbank on the rate of turn output signal of said rate of turn gyro.

4. A rate' of turn.. instrument having'an indication'propoitional tothe rate of turn in lazimuth of the craft onuwhich it is mounted, comprisinga rate of turngyro, an indicator operated thereby, an accelerationsensitivemeans responsive tothe resultant acceleration ofA said craft along `thev ver- 8 tical craft axis and adapted to have a displace'-1 ment along said axis proportional to a function of the bank angle lof said craft, a motion transmitting means for operatively connecting said rate gyro and said indicator, and means 4controlled by said acceleration means for varying the motion transfer ratio of said transmitting means,.-v

5. ln a rate of turn instrument adapted -to give an output signal proportional tothe rate of turn in azimuth of the craft on which it is mounted,r

the combination with a rate of turn gyro having an output signal, a source of voltage, an acceleration sensitive member sensitive lto the resultant acceleration of said craftV along the vertical craft axis, of means connected with said voltage source and operated by said acceleration sensitive member for supplying a voltage output dependent vin magnitude on said resultant acceleration, vand means for combining said voltage output-.with said gyro output signal, whereby to vary said gyro output signal in accordance with said resultant acceleration.V d

6. In a rate of turn instrument adapted to give an output signal proportional to the azimuthal rate of turn of the craft on which it is mounted, the combination with a rate of turn gyro, of a source of voltage, of a first variable transformer responsive to movement of said gyro, of an acceleration sensitive means sensitive to the resultant acceleration of said craft along the vertical craft axis and adapted to have a displacement proportional to said resultant acceleration, of a second variable Vtransformer connected to said voltage source and operated by said acceleration sensitive means for producing an output proportional to said displacement, said second transformer output being connected to said first transformer whereby the voltage output of said second transformer controls the voltage output of said first transformer.

7. A rate'of turn indicator having an output.

tical craft axis for providing an output dependent upon bank angle of the craft, and means connecting the-output of said acceleration sensitive means with said indicator-.connecting -means for effecting an operation'of said indicator in accordance with the output of said rate gyro modified by a function of craft bank angle.

8. In an instrument of the character described for dirigible craft, the combination with means for measuring the rate of turn of the Vcraft about the vertical axis thereof, an indicator, means for connecting the output of said rate measuring means to operate said indicator, an acceleration sensitive meansy responsive to the resultant acceleration of said craft along the vertical craft axis; for providingV an output dependent upon` bank angle of the craft, and means connecting the output of said acceleration sensitive means with saidI indicator-connecting means for velfecting an operation of said indicator in accordance with theV output of said rate gyro modified by a function of craft bank angle v 9. in an instrument of the character described fondirigiblecraft, thercombination with means' .for measuring the rate of turn of the craft about the yertical axis thereof, an indicator, meansfor connecting the output of said rate measuring .REFERENCES CITED means to operate said indicator, an acceleration The following references are of record n the sensitive means responsive to the resultant acce1 me of this patent:

eration of said craft along the vertical craft axis for providing an output dependent upon bank 5V UNITED STATES PATENTS angle of the craft, and means connecting the outl Number Name Date put of said acceleration sensitive means with said Re, 22,33() Draper June 8, 1943 indicator-connecting means for effecting an oper- 1,924,037 Henderson Aug. 22, 1933 ation of said indicator in accordance with the FOREIGN PATENTS output of said rate gyro modified by a secant 10 function of craft bank angle. i Number Cuntry Date WALTER'WRIGLEY, 329,122 Italy Sept. 2, 1935 

